Sun Java System Web Server 6.1 SP9 Performance Tuning, Sizing, and Scaling Guide

Keep-Alive Connections Flushed

A web site that might be able to service 75 requests per second without keep-alive connections may be able to do 200-300 requests per second when keep-alive is enabled. Therefore, as a client requests various items from a single page, it is important that keep-alive connections are being used effectively. If the KeepAliveCount exceeds the MaxKeepAliveConnections, subsequent keep-alive connections will be closed, or "flushed," instead of being honored and kept alive.

Check the KeepAliveFlushes and KeepAliveHits values using statistics from perfdump or the Monitor Current Activity page of the Server Manager. For more information, seeKeep-Alive/Persistent Connection Information

On a site where keep-alive connections are running well, the ratio of KeepAliveFlushes to KeepAliveHits is very low. If the ratio is high (greater than 1:1), your site is probably not utilizing keep-alive connections as well as it could.

To reduce keep-alive flushes, increase the MaxKeepAliveConnections value in the magnus.conf file or the Magnus Editor of the Server Manager. The default value is 256. By raising the value, you keep more waiting keep-alive connections open.

Caution – Caution –

On UNIX/Linux systems, if the MaxKeepAliveConnections value is too high, the server can run out of open file descriptors. Typically 1024 is the limit for open files on UNIX/Linux, so increasing this value above 500 is not recommended.